In an ordinary carburetor, fuel is introduced through an idle port when the engine is idled, through a slow port when it is driven at low speeds, and through a main nozzle when it is driven at high speeds. In carburetors of this conventional type, however, it is difficult to attain a correct air-fuel ratio due to shortage of fuel, especially in a transitional state between the low-speed and high-speed operational phases. Particularly, when such transition occurs abruptly, it is difficult to obtain a correctly proportioned fuel-air mixture, thus causing non-uniform rotation of the engine. Therefore, in order to prevent such fuel shortage during acceleration, ordinary carburetors have been equipped with an accelerating pump which supplies fuel interlockingly with the rotation of a throttle valve shaft. By thus supplying fuel to a stream of sucked air when accelerating, that is, when the vehicle accelerator pedal is depressed, the delay in fuel supply response during acceleration and the diluting of fuel-air mixture in the transitional region have been at least partially prevented.
However, since it is operated mechanically, such conventional accelerating equipment is slow to respond so that it also causes some delay in supplying the necessary fuel to the air intake passage. Therefore, it has been impossible to perfectly prevent the transitional dilution of the fuel-air mixture.
An object of this invention is to provide a compensation apparatus for correcting the defective delay in response produced by the conventional mechanically operated accelerating pump, and, further, for preventing the shortage of fuel in the transitional region between the low-speed and high-speed operational phases.
Another object of this invention is to provide a compensation apparatus for discharging fuel directly in response to the opening of the throttle valve.
The compensation apparatus of this invention provides a first opening in the wall of the air intake passage near the edge of the throttle valve so that the first opening is positioned upstream or downstream of the throttle valve depending on the degree of opening thereof. A second opening is similarly provided in the wall of the air intake passage so that it is positioned downstream of the throttle valve, at least when the first opening is positioned upstream thereof. A connecting passage joins the first and second openings, and a further passage supplies fuel to the connecting passage.
According to this invention, as described above, air is reversely bled through the first opening and fuel is discharged through the second opening, whereby fuel shortage due to response delay in the transitional region between the low-speed and high-speed phases, or in the transitional region between the idling and the low-speed phase, is prevented.